There are so many kinds of birds in the world, and most of them are small and light, designed to take to the sky with ease.

Some birds are larger, of course, but how large can one be and still take flight?

It turns out, about the same weight as 300 tennis balls.

The male kori bird (Ardeotis kori) weighs between 24-40 pounds, with a wingspan of around 9 feet. The females are roughly half that size, according to the Smithsonian National Zoo.

The largest confirmed specimen weighed 40 pounds and was killed in South Africa in 1936.

They live in two distinct ranges, one in South and the other in East Africa, and spend most of their time foraging on the ground. Their diet includes insects, reptiles, small rodents, seeds, berries, and roots.

The birds are listed as “near threatened,” and are described as “largely sedentary, but does undertake local movements.”

The second heaviest flying bird is the great bustard (Otis tarda), which weighs in at an impressive 13-39 pounds. They don’t remain local, but undertake a round trip migration of around 2,485 miles between their breeding grounds in Mongolia and their wintering grounds in China.

The world’s heaviest bird that can’t fly is the common ostrich. It can weigh up to 343 pounds.

There’s no way you’re going to see one of those flying high.

If I saw a 40-pound flying bird I might assume I’d stumbled into Jurassic Park.

If you thought that was interesting, you might like to read about why we should be worried about the leak in the bottom of the ocean.